The Combination Of Static And Dynamic Method And It's Application In Steel Truss Damage Detection

Structures serving in complicated environment often suffer from different kinds of damages and deterioration. With the accumulation of damages, sudden collapse may happen and cause great loss of lives and property. So it makes great sense to detect the damages of structures in time. In this thesis, vibration based damage detection theories and methods are discussed, a new method which combines the static test and dynamic test is proposed and studied in detail. The Symmetrical Signal Method (SSM) is used for determination of damage location. This thesis can be summarized as follows:(1) A steel truss model with length of 8 meters long is setup, by replacing elements with different cross sections; twelve truss models representing different extent of damage are obtained.(2) All the 12 models are tested statically and dynamically to measure their load-displacement curves and mode parameters.(3) The truss models are simplified as simple support beams with concentrated mass at mid span. The relationship between first mode frequency and stiffness is regressed. And this relationship can be used to extrapolate static behavior of structure.(4) A linear equation between stiffness and the square of frequency obtained by regressing of test data from twelve models, thus the resolution of this new method is determined.(5) The Symmetrical Signal Method (SSM) is used to find the exact location of the damage.